MIDI track recorded with a bass line. Edited/corrected by hand. Sounds good. There is plenty of other stuff around it in other tracks, audio and MIDI.
This particular MIDI track is verified with MIDI Tracer. NoteOn properly followed by NoteOff as expected. (There is no overlap.) Next step is to commit the track to audio.
Setup: MIDI track is soloed, output goes to external synth. Audio goes back to Ardour, to a new audio track. Arm recording. Start.
Expect: Bass line played back as recorded, recorded to audio track.
Actual: First 1-2 notes drop their NoteOff and linger for some time. Confirmed in MIDI Tracer, NoteOff lacking. List Editor shows very long duration. The problem persists even if I manually edit the duration of the first notes.
When listening without recording it mostly sounds ok, except sometimes it happens even then.
Workaround: Add a few notes several bars before the real track so they have time to die out. Kludgy but worked.

Additional Information

It's an all-USB MIDI and audio setup. Audio goes to the USB connector of a Behringer mixer.

Activities

This happens on a regular basis. Playback from MIDI without problem. Recording (bouncing to audio): the first notes hangs (keeps sounding). New workaround: Start transport (typically space bar), hit Shift-R (record) while it is running.